Atomizing furnaces typically comprise a graphite tube which essentially forms the tube furnace apparatus. The graphite tube comprises graphite contacts which are disposed on the graphite tube such that high currents can run via the graphite tube in longitudinal or transverse direction in order to heat the graphite tube. Within the graphite tube a sample carrier is disposed, which can also be formed from graphite. On the sample carrier an analyte or sample can be placed, which is heated to a temperature high enough for the sample to be atomized. In order to identify the proportions of the elements of the sample, a measuring light beam is sent through a longitudinal drill hole in the tube furnace part. It is substantial for the measuring results that no electric heating current be running through the sample carrier. Further it must be avoided that the sample carrier is directly heated by heat conduction via a contact with the graphite tube. Additionally, a stable fixation of the sample carrier within the tube furnace apparatus is necessary in order to avoid a displacement of the sample carrier in relation to the tube furnace apparatus or a tilting of the sample carrier.
From DE 199 32 874 C2 an atomizing furnace is known in which a sample carrier is disposed within a tube furnace apparatus and punctually supported on a wall of the tube furnace apparatus by three or four supporting protrusions. The supporting protrusions therein are formed in a middle of the sample carrier on its circumference in relation to a length of the sample carrier. The supporting protrusions are further disposed in three planes that run transversally to a longitudinal axis of the sample carrier.
In the afore described sample carrier a relatively low heat conduction via the supporting protrusions is provided, thus enabling a particularly good indirect heating of the analyte, as opposed to comparably large supports that could for example be formed as a ring on the circumference of the sample carrier or in the form of a beam. Consequently, any enlargement of the supporting protrusions or of their contact area to the tube furnace apparatus leads to an improved direct heat conduction, which here is undesirable, in particular for an analysis. Further, the alignment of the supporting protrusions of the known sample carrier is disadvantageous since in the case of a transverse heating, meaning a feeding of power on the tube furnace apparatus transversally to the longitudinal axis of the tube furnace apparatus, a particularly good current flow through the sample carrier is given. This can be largely eliminated for the position of the supporting protrusions in the middle of the sample carrier for a longitudinal heating, meaning feeding power into the respective ends of the tube furnace apparatus, since then the supporting protrusions have the same electric potential. Yet it is desirable that the sample carrier and the atomizing furnace be suitable for both transverse and longitudinal heating. Another disadvantage that arises from the alignment of the supporting protrusions in the sample carrier of DE 193 28 74 C2 is the static support of the sample carrier of the tube furnace apparatus. Since the supporting protrusions are formed in the middle of the sample carrier, the sample carrier can easily tilt in relation to the tube furnace apparatus. This particularly pertains to a correct positional assembly and fixation of the sample carrier within the tube furnace apparatus.